The present invention relates generally to earth excavating equipment, and more particularly provides an improved flex pin that is used to captively retain a replaceable excavating tooth point on the nose portion of an adapter which, in turn, is secured to the forward lip of an excavating bucket or the like.
Excavating tooth assemblies provided on digging equipment such as excavating buckets or the like typically comprise a relatively massive adapter portion which is suitably anchored to the forward bucket lip and has a reduced cross-section, forwardly projecting nose portion, and a replaceable tooth point having formed through a rear end thereof a pocket opening that releasably receives the adapter nose. To captively retain the point on the adapter nose, aligned transverse openings are formed through these interengageable elements adjacent the rear end of the point, and a device commonly referred to as a flex pin is driven into these openings.
While flex pins have a variety of configurations, a widely used version, as representatively illustrated in U.S. Pat. No. 3,526,049 to Nichols and U.S. Pat. No. 3,685,178 to Ratkowski, typically comprises elongated, straight metal locking and wedge members which are laterally spaced apart and intersecured by an elongated central elastomeric element. As the flex pin is being driven into the aligned point and adapter nose openings the elastomeric element is compressed and, when the pin is driven to its installed position, laterally urges a detent portion formed on one of the two metal portions of the pin into engagement with a suitably configured portion of the adapter nose to captively retain the flex pin within the point and adapter openings. With the flex pin in its operative position within such openings, the elastomeric element is in a state of partial compression, rear surfaces of the tooth point openings bear against opposite end portions of the locking member, and a forward surface of the adapter nose opening bears against a longitudinally central portion of the wedge member. Forwardly directed tooth point removal forces encountered during the excavating process cause the tooth point to be driven forwardly relative to the adapter to thereby move the locking member closer to the wedge member and further compress the central elastomeric element, the opposite ends of the locking member preventing forward removal of the tooth point.
Two primary problems and disadvantages are present in this type of conventional flex pin construction--each of which is related to failure of the central elastomeric element. First, as the flex pin is being driven into the aligned tooth point and adapter nose openings the locking and wedge members tend to be moved longitudinally relative to one another. Thus, if the driving-in process is not carefully performed, this relative longitudinal movement can easily shear the elastomeric element, thereby ruining the flex pin. Secondly, excessive forwardly directed tooth point removal loads can laterally move the locking member close enough to the wedge member to overcompress and thereby split the elastomeric element.
Various attempts have previously been made to better protect the critical central elastomeric portion of the flex pin by altering the essentially straight configurations of the locking and wedge member portions utilized in flex pin structures such as those depicted in the Nichols and Ratkowski patents. One such proposed solution, as exemplified in U.S. Pat. No. 4,192,089 to Schwappach and U.S. Pat. No. 4,446,638 to Novotny et al, is to form a central lateral recess in a front side portion of the locking member and to shorten the wedge member so that it is laterally movable into such recess against the resilient force of the central elastomeric element. With the elastomeric element in an uncompressed condition the opposite ends of the wedge member underlie the opposite end surfaces of the recess so that as the flex pin is being driven into the point and adapter openings one of the wedge member ends is driven into engagement with its adjacent recess end surface. This limits the relative longitudinal travel between the locking and wedge members to thereby limit the shear stress imposed upon the elastomeric element.
In an attempt to similarly limit the lateral compressive stress imposed on the elastomeric element, the maximum distance which the wedge member may be laterally moved into the locking member recess is limited to a distance less than the front-to-rear thickness of the elastomeric element by causing opposite end portions of the wedge member to rigidly engage portions of the locking member during travel of the wedge member into the locking member recess. In the Schwappach patent this inward travel limitation is achieved by forming on the opposite wedge member ends rearwardly directed projections which are engageable with the rear side surface of the locking recess. In the Novotny et al patent a similar result is achieved by forming forwardly facing shoulders positioned adjacent opposite ends of the recess which are adapted to rigidly engage opposite end portions of the wedge member during its lateral travel into the recess. Somewhat similar schemes for protecting elastomeric flex pin portions are evidenced in U.S. Pat. No. 2,927,387 to Drover and U.S. Pat. No. 3,126,654 to Eyolfson et al.
While this conventional method of limiting lateral compression of the elastomeric element represents an improvement over somewhat simpler flex pin structures such as those depicted in the Nichols and Ratkowski patents, it creates significant structural problems in the wedge member. Specifically, when the wedge member is moved to its "stopped" position within the locking member recess a large rigid bending load is imposed thereon by the forward surface of the adapter nose opening which bears against a central rear side portion of the wedge member. To adequately strengthen the wedge member against such bending load it is necessary to appropriately increase its front-to-rear thickness. This thickening, in turn, typically requires that undesirable design modifications be made to one or all of the elastomeric element, the locking member and the adapter nose opening.
Specifically, it is well known that the overall strength of an adapter nose is, generally speaking, inversely proportional to the size of the flex pin opening formed therethrough. Thus, if it desired to maintain a given front-to-rear length of the adapter nose opening, the necessary thickening of the wedge member requires that the front-to-rear thickness of one or both of the elastomeric element and the locking member be correspondingly reduced. Reducing the thickness of the locking member, of course, structurally weakens the flex pin, while reducing the thickness of the elastomeric element reduces the resiliency of the flex pin and the potential lateral travel between its rigid elements. Of course, neither of these results is desirable.
If, on the other hand, the front-to-rear thicknesses of the elastomeric element and the locking member are maintained, the thickening of the wedge member requires that the front-to-rear length of the adapter nose opening be correspondingly increased. This, of course, undesirably weakens the adapter nose.
In view of the foregoing, it is accordingly an object of the present invention to provide improved resilient flex pin apparatus which eliminates or minimizes the above-mentioned and other problems, limitations and disadvantages heretofore associated with flex pins of conventional design and construction.